SULFUR SYMBOL:฀S฀ PERIOD:฀3฀ GROUP:฀16฀(VIA)฀ ATOMIC฀NO:฀16

SULFUR SYMBOL:฀S฀ PERIOD:฀3฀ GROUP:฀16฀(VIA)฀ ATOMIC฀NO:฀16

ATOMIC฀MASS:฀32.065฀amu฀ VALENCE:฀2,฀4,฀and฀6฀ OXIDATION฀STATE:฀–2,฀+4,฀and฀ +6฀ NATURAL฀STATE:฀Solid ORIGIN฀OF฀NAME: ฀From฀the฀Sanskrit฀word฀sulvere฀and฀the฀Latin฀word฀sulphurim. ISOTOPES:฀There฀are฀a฀total฀of฀24฀isotopes฀of฀sulfur;฀all฀but฀four฀of฀these฀are฀radioactive.฀

The฀four฀stable฀isotopes฀and฀their฀contribution฀to฀sulfur’s฀total฀abundance฀on฀Earth฀are฀ as฀follows:฀S-32฀contributes฀95.02%฀to฀the฀abundance฀of฀sulfur;฀S-33,฀just฀0.75%;฀S-34,฀ 4.21%;฀and฀S-36,฀0.02%.

ELECTRON฀CONFIGURATION ฀ Energy฀Levels/Shells/Electrons฀ Orbitals/Electrons

s2,฀p6

฀ 3-M฀=฀6฀

s2,฀p4

Properties Sulfur is considered a nonmetallic solid. It is found in three allotropic crystal forms:

1. Orthorhombic (or rhombic) octahedral lemon-yellow crystals, which are also called “brimstone” and referred to as “alpha” sulfur. The density of this form of sulfur is 2.06 g/cm 3 , with a melting point of 95.5°C. 2. Monoclinic, prismatic crystals, which are light-yellow in color. This allotrope is referred to as “beta” sulfur. Its density is 1.96 g/cm 3 , with a melting point of 119.3°C. 3. Amorphous sulfur is formed when molten sulfur is quickly cooled. Amorphous sulfur is soft and elastic, and as it cools, it reverts back to the orthorhombic allotropic form.

Sulfur, in its elemental form, is rather common and does not have a taste or odor except when in contact with oxygen, when it forms small amounts of sulfur dioxide.

235 Characteristics

Guide to the Elements |

Sulfur exhibits a remarkable array of unique characteristics. Today, there are chemists devoting large portions of their careers to studying this unusual element. For example, when sulfur is melted, its viscosity increases, and it turns reddish-black as it is heated. Beyond 200°C, the color begins to lighten, and it flows as a thinner liquid.

Sulfur burns with a beautiful subdued blue flame. The old English name for sulfur was “brimstone,” which means “a stone that burns.” This is the origin of the term “fire and brim- stone” when referring to great heat. Above 445°C, sulfur turns to a gas, which is dark orange- yellow but which becomes lighter in color as the temperature rises.

Sulfur is an oxidizing agent and has the ability to combine with most other elements to form compounds.

Abundance฀and฀Source Sulfur has been known since ancient times primarily because it is a rather common sub-

stance. It is the 15th most common element in the universe, and though it is not found in all regions of the Earth, there are significant deposits in south Texas and Louisiana, as well in all volcanoes. Sulfur makes up about 1% of the Earth’s crust.

Sulfur is an element found in many common minerals, such as galena (PbS), pyrite (fool’s gold, FeS 2 ), sphalerite (ZnS), cinnabar (HgS), and celestite (SrSO 4 ), among oth- ers. About 1/4 of all sulfur procured today is recovered from petroleum production. The majority of sulfur is the result of or a by-product of mining other minerals from the ores containing sulfur.

Sulfur is mined by the recovery method known as the Frasch process, which was invented by Herman Frasch in Germany in the early 1900s. This process forces superheated water, under pressure, into deep underground sulfur deposits. Compressed air then forces the molten sulfur to the surface, where it is cooled. There are other methods for mining sulfur, but the Frasch process is the most important and most economical.

Sulfur is found in Sicily, Canada, Central Europe, and the Arabian oil states, as well as in the southern United States in Texas and Louisiana and offshore beneath the Gulf of Mexico.

History Sulfur was known in the days of early humans. No single person can take credit for its

discovery. It was probably one of the first “free” elements ancient humans tried to use and understand besides the “always known” air, fire, and water.

Sometime around 1300 BCE, an unknown alchemist described sulfuric acid. Not much is known about the early use of sulfur or sulfuric acid. In 1579 an alchemist named Andreas Libavius described the progress of alchemy. In his book he described how hydrochloric and sulfuric acids are produced and mentioned the formation of aqua regia, which is a mixture of acids that is strong enough to dissolve gold—the royal metal.